This invention relates to a container, particularly a container for shipping liquids, and to a method for protecting a liquid from the environment during shipping.
Many liquid resin or adhesive systems such as moisture-curable polyurethane polymers (e.g., sealant primers) or polyurethane prepolymers solidify or cure upon exposure to air or moisture. Therefore, it is desirable to minimize contact between these liquids and the environment prior to their end-use application. While exposure to the environment is more or less of a problem depending on the liquid resin or adhesive system employed, the problems associated with premature contact with the environment are aggravated by long periods between preparation of the liquid resin or adhesive and its actual use. This is a particular problem when the liquid resin or adhesive is shipped over long distances or is maintained in the shipping container for long periods of time prior to use.
In a conventional operation, the liquid resin or adhesive is placed in a metal drum, commonly a 55 gallon or larger drum, often lined with a plastic film adhered to the inner metal layer to prevent corrosion and contamination of both the drum and the liquid. The drum is covered with a metal or plastic-coated metal top having approximately the same size as the drum body which is locked to the drum using a locking collar or bung. The means for securing the metal lid or top to the drum body is not particularly effective in preventing the contact of the environment with the drum contents. As such, portions of the liquid resin or adhesive solidify or cure and, upon removal, the solid or cured material is removed with the liquid; thereby introducing impurities into the finished article. It is also necessary to clean the drum after each use. In addition, disposing the metal drum may result in both economic loss and environmental damage.
A filler of a fusible plastic such as polyethylene is often placed in the drum to contain the liquid resin or adhesive and the fusible plastic is then sealed such as by heating or by merely using a tie (see for example U.S. Pat. No. 3,940,052). This provides a more effective barrier between the environment and the contained liquid but, when stored for long periods of time or shipped over long distances, the barrier is not suitable for many applications. In addition, the loose plastic fillers are not easily handled.
Yet another method for shipping a liquid resin or adhesive involves disposing an inner liner of a plastic material having the general shape of the drum which is commonly a paperboard or fiberboard drum against the walls and top of the drum and gluing or otherwise adhering the plastic to the interior surface of the drum (see, for example European Patent Application No. 0 501 015). Alternatively, U.S. Pat. No. 4,347,948 teaches a container in which a plastic inner liner is employed which extends beyond the top of the drum. A typical inner liner consists of an elastic plastic film, including thermoplastic plastic such as polyethylene, polypropylene, polyester, or nylon, as well as compound films such as the plastic with another material (e.g., paper, cloth or metal foil) laminate having layers of polyethylene, metal foil and polyester with the polyethylene layer being closest to and bonded to the interior surface of the drum. The cover or lid comprises a body, a plastic sheet and a ring packing so as to make it possible to seal the container body to be air-tight. These containers do not eliminate the problems associated with premature curing or solidification.
Alternatively, a drum having a plastic inner liner (e.g., a laminate of plastic and metal foil) extending beyond the top of the drum is filled with the liquid to be stored or shipped. Once filled, a plastic (e.g., polyethylene) film, larger than the opening in the drum, is placed over the top of the liquid and the drum sealed using a metal or paper top or lid placed over the polyethylene film. The excess portions of the top film and inner liner contact each other above the liquid layer to seal the container. The problems associated with premature curing or solidification, while reduced, are not eliminated. Upon shipping or storage, the liquid near the seal can solidify or cure, with cured or solidified lumps or droplets contained in the bulk of the liquid material,
In view of the stated deficiencies of the prior art, it remains desirable to provide a container for liquid resins and adhesives which reduces or minimizes contact of the resin or adhesive with the drum and the environment (air and moisture) during shipping or storage. Such a container which facilitates easy reuse of the outer drum without complex cleaning steps is desirable.